1. Technical Field
The present invention relates to a motor drive apparatus for driving, for example, a motor for opening and closing a window of a vehicle.
2. Related Art
FIG. 28 is a block diagram showing a power window apparatus for performing open/close control of a window of a vehicle. An operation switch 40 is a switch for opening and closing a window 50. A motor drive apparatus 41 drives a motor 58 based on operation performed on the operation switch 40, and controls, e.g., the rotational direction and the rotational speed of the motor 58. When the motor 58 rotates, a window open/close mechanism (which will be described later) that works together with the motor is activated to open or close the window 50. A rotary encoder 59 outputs a pulse in synchronization with the rotation of the motor 58. The motor drive apparatus 41 calculates, e.g., the rotational speed of the motor 58 from this pulse to control the rotation of the motor 58.
FIG. 29 is a schematic configuration view showing an example of operation switch 40. The operation switch 40 includes an operation knob 71 that can pivot about an axis Q in the ab-direction, a rod 72 arranged integrally with this operation knob 71, and a switch mechanism 73 having a contact (omitted from the figure). Numeral 74 denotes an actuator of the switch mechanism 73, and numeral 70 denotes a cover for a switch unit accommodating the operation switch 40. The lower end of the rod 72 is engaged with the actuator 74. When the operation knob 71 rotates in the ab-direction, the actuator 74 moves in the cd-direction via the rod 72, and according to the moved position, the contact of the switch mechanism 73 is switched.
The operation knob 71 is switchable to each of positions of automatic close AC, manual close MC, neutral N, manual open MO, and automatic open AO. In FIG. 29, the operation knob 71 is at the position of the neutral N. When the operation knob 71 is rotated a certain amount in the a-direction from the position of the neutral N to be brought to position of the manual close MC, a manual close operation in which the window is closed in a manual mode is performed. When the operation knob 71 is further rotated in the a-direction from the position of the manual close MC to be brought to the position of the automatic close AC, an automatic close operation in which the window is closed in an automatic mode is performed. On the other hand, when the operation knob 71 is rotated a certain amount in the b-direction from the position of the neural N to be brought to the position of the manual open MO, a manual open operation in which the window is opened in the manual mode is performed. When the operation knob 71 is further rotated in the b-direction from the position of the manual open MO to be brought to the position of the automatic open AO, an automatic open operation the window is opened in the automatic mode is performed. The operation knob 71 is arranged with a spring (not shown). With the force of the spring, the operation knob 71 returns back to the position of the neutral N when a hand is released from the rotated operation knob 71.
In the manual mode, the close operation or open operation of the window is performed only while the operation knob 71 is held by the hand at the position of the manual close MC or the manual open MC. The close operation or open operation of the window is halted as soon as the hand is released from the operation knob 71 and the knob returns back to the position of the neutral N. In contrast, in the automatic mode, once the operation knob 71 is operated and brought to the position of the automatic close AC or the automatic open AO, after that the close operation or open operation of the window continues even if the hand is released from the operation knob 71 and the knob returns back to the position of the neutral N.
FIG. 30 is a view showing an example of window open/close mechanism arranged on each window of a vehicle. A window glass 51 moves upward/downward upon activation of the window open/close mechanism 52. The window open/close mechanism 52 includes a support member 53, a first arm 54, a second arm 55, a bracket 56, a guide member 57, a pinion 60, and a gear 61. The support member 53 is attached to the lower end of the window glass 51. The first arm 54 is engaged with the support member 53 at one end, and is rotatably supported by the bracket 56 at the other end. The second arm 55 is engaged with the support member 53 at one end, and is engaged with the guide member 57 at the other end. The middle sections of the first arm 54 and the second arm 55 are coupled with each other via a shaft. The pinion 60 is rotationally driven by the motor 58. The motor 58 is coupled with the rotary encoder 59. A fan-shaped gear 61 is fixed to the first arm 54, and meshes with the pinion 60. When the motor 58 rotates, the pinion 60 and the gear 61 rotate, and the first arm 54 pivots. With this movement, the other end of the second arm 55 slides along the groove of the guide member 57 in the lateral direction. As a result, the support member 53 moves in the vertical direction, so that the window glass 51 moves upward/downward, and the window 50 opens or closes.
In the above-described power window apparatus, the motor 58 is driven in a normal rotation direction or in a reverse rotation direction according to the operation of the operation switch 40, and accordingly the window 50 opens and closes. For example, when the motor 58 is driven in the normal rotation direction, the window 50 opens. When the motor 58 is driven in the reverse rotation direction, the window 50 closes. A control circuit (omitted for the figure) of the motor drive apparatus 41 switches the direction of the current flowing in the motor 58, so as to control the normal rotation and the reverse rotation of the motor 58. Conventionally, a mechanical relay (contact relay) has been used as this switching means.
In general, a power window apparatus is equipped with a wetting detection circuit so as to prevent malfunction of the motor when rainwater enters into the apparatus or the apparatus is submerged into water. When the wetting detection circuit detects wetting, and the operation switch performs the open operation of the window, the control circuit rotates the motor in the normal rotation direction based on the normal rotation instruction signal provided by the operation switch and the detection signal provided by the wetting detection circuit. Therefore, the open operation of the window can be normally performed.
Japanese Unexamined Patent Publication Nos. 2000-120330 and 2005-65442 describe a power window apparatus having a wetting detection circuit and a control circuit using a mechanical relay for switching a normal rotation and a reverse rotation of a motor as described above.